• Proceedings of the KSME Conference
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• 2008.11a
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• pp.244-249
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• 2008

It happened a failure on special bolt which supported main landing gear actuator up-lock rod of 00 aircraft. Fracture was occurred at end of center drilled hole and thread machined on bolt. Metallographic, fractographic, and other characteristics of embrittlement analysis and experiments carried out on the failed bolt to find out the reason. Bolt surface was cadmium electroplated(EP) to give lubrication and provide excellent corrosion resistance. Resultly, Bolt was failed due to cadmium embrittlement occurred during baking treatment as well as center drilled hole. for the failure that are relevant to failure analysis and prevention. For their successful functional application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and is complete with no center drilled hole

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.769-774
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• 2010

It happened fractures on special bolt which supported main landing gear actuator up-lock rod of aircraft. Cracks were initiated mainly from the center hole and the external thread of the special bolt. To find out failure root causes, metallographic, fractographic analyses as well as test work were carried out. From the fractographic study by SEM work, fracture occurred by a brittle intergranular type failure. The fracture could be occurred primarily by solid-metal-induced embrittlement due to cadmium embrittler penetrated into the flaw existed after machining work for center hole and thread on the bolt during baking treatment processing to eliminate hydrogen. For its successful application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and make no more drilled center hole on the bolt to prevent same failure.

• Corrosion Science and Technology
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• v.10 no.4
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• pp.131-135
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• 2011

The demands of high-strength steel have been steadily increased to reduce the weight of vehicles. Although the TRIP steel has been the promising candidate material for the purpose, high strength hinders the application due to the susceptibility to hydrogen delayed fracture in the corrosive environment. Moreover, the testing method was not specified in the ISO standards. In this work, the test method to evaluate the susceptibility of hydrogen delayed fracture was studied by slow strain rate testing technique. The four test experimental parameters were studied : strain rate, hydrogen charging time, holding time after hydrogen charging, and holding time after cadmium plating. The steel was fractured by hydrogen in case the strain rate was in the range of $1{\times}10^{-4}{\sim}5{\times}10^{-7}/sec$. It was confirmed that the slow strain rate test is effective method to evaluate the susceptibility to hydrogen delayed fracture. The holding time over 24 hrs after hydrogen charging, nullified the hydrogen effect, that is, the specimen was no more susceptible to hydrogen after 24 hrs even though the specimen was fully hydrogen-charged. Moreover, cadmium electroplating could not prevent from diffusing out the hydrogen from the steel in the experiment. The effective experimental procedures were discussed.

• Journal of the Korean Institute of Gas
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• v.26 no.3
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• pp.21-26
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• 2022

Zinc is emerging as a environment-friendly plating material to replace cadmium, which is harmful to the human body, to prevent hydrogen gas penetration or release from metal materials. Electroplating of Zn and Zn alloys, which is usually performed in an aqueous acidic atmosphere, has disadvantages such as low coulombic efficiency, corrosion, and hydrogen release, resulting in industrial use difficult. In this study, a deep-eutectic solvent was synthesized using choline chloride and ethylene glycol. Using this as a solvent, an electrolyte for Zn plating was prepared, and then zinc was plated on the STS 304 substrate. The surface microstructure and roughness were observed using SEM and AFM. The crystal structure of the electro-plated film was analyzed using XRD. Finally, the preventing effects of hydrogen release through Zn-based deep-eutectic plating on the STS 304 substrate were compared with the uncoated substrate.